The basic operation of the HTML formatter is that it takes an AST as input, and outputs a whole bunch of .html and .png files to an output directory. These files can either be all in the one directory or ordered into nested subdirectories (see the file_layout option). The output is created by individual modules called "Pages", and like other parts of Synopsis you specify a list of these and they are executed in order. Each page generates a type of output, such as a frames index, the pages for classes and namespaces, an inheritance graph, the tree of modules to go in the corner frame, the index of individual modules to go in the left frame, etc.

The order of pages is generally not important, but there are some effects: pages compete for index pages, such as which page gets to write the "index.html" page, which page gets to be the default page for the top-left frame, which page gets to be default for the left frame, etc. The Page which asks for one of these first, gets it, which is why FramesIndex usually comes first.